left sidechest pian

What other symptoms do you have?  Do you have heartburn frequently at all?  Have you been doing any strenuous activity recently?  I know commonly people with frequent heartburn can develop chest pain from a burned esophagus.  Or anyone who has been doing a lot of heavy lifting may pull muscles in their pectoral muscles that didn't hurt during the activity but hurts much later.  Is it a pain that is a burning type of pain or sharp?  If you do not get better in a day or so, you should see a doctor to make sure it isn't something serious.